Functional Photosystem II reaction centers were isolated from the thermophilic cyanobacterium Phormidium laminosum and reconstituted in dimyristoyl-phosphatidyl-choline (')MPC) vesicles. Samples with the maximum protein/lipid ratio were examined in the STEM, both as freeze-dried and negatively stained specimens. The freeze-dried samples showed a number of folded structures (perhaps due to the vesicles breaking up) and because of this, there was little order in the stained samples. Further experiments to preserve the structures are planned.